If you are going to have firearms aboard your boat, and you are going to venture into the waters belonging to other governments, I strongly encourage you to learn how to deep-six your stuff in ways so that they cannot be recovered. You also need to do the deep-six-ing in international waters in a way that will not draw attention to your actions as polluting the seas.
If you are going to cruise the east coast you will need to know the state boundaries as they apply to how far from average high-tide seaward, as well as any wierd zigs or zags from coastal reference points. For example, the Chesapeake Bay is "governed" by about 6 states and their various firearms laws, as well as by USCG/Homeland Insecurity/ICE and perhaps some taskforce of the month.
You may also want to get up-to-date on the favored drug smuggling routes so as to avoid them. Cruising can get awfully interesting when you get visited by black rubber boats. Houseboating on the Great Lakes can be exciting when you explore various coves & inlets that "happen to be" within some undetermined nearness to Canadian waters or shores.
Do NOT try to hide anything from the JBTs who board you to conduct various safety and/or customs searches. Do NOT engage in "repel boarders" drills as they are approaching. And DO NOT allow anyone to "slip over the side" as they are heading your way - that airborne FLIR you never spotted will be a source of never-ending grief for somebody.
In spite of all this, 12-guage slugs in the magazine for standoff work and 00, 000 or #4 buckshot for social distances are all decent recommendations. Flare guns work just fine, but are nowhere near as accurate as shown in the movies. A short, stout boat rod rigged with 250# line and a snap-on rig of half a dozen or so treble hooks can serve as either a grapple or as moving razorwire as well as a trotline for lunch/dinner. Be creative, and remember that you will have limited room to swing anything.
Check with the local marine LEO outfit to lear what the biggest problems are encountering. I suspect it will be boating while intoxicated and failure to carry required safety devices. Unless you are runing an open-ocean fastmover, there is likely to be little that will attract the attention of the unsavory to you. (But it never hurts to be prepared.)
stay safe.
skidmark